code 455 after replacing intake gaskets what do i need to look for to fix? on 1997 Ford F-150

replaced gas cap replaced cat. convertor. replace the vavle at cannister. had evap test can find smoke can it be another vavle or a sensor that is not reading on codes? cannister control vavle maybe. before replacing intakes had a misfire all the time losing alittle bit of radiaor fliud but not now.

Asked by for the 1997 Ford F-150